Question the-st

3.4 Two-Variable Data & Models - Line of best fit
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  • The sterplot has 10 data points.
  • The data points are in a linear pattern trending down from left to right.
  • Select data points have the following approximate coordinates:
    • (0.8 comma 8.9)
    • (2.8 comma 5.1)
    • (4.1 comma 2.9)

Which of the following equations is the most appropriate linear model for the data shown in the sterplot?

A.

y = - 1.9 x - 10.1

B.

y = - 1.9 x + 10.1

C.

y = 1.9 x - 10.1

D.

y = 1.9 x + 10.1

The sterplot has 10 data points. The data points are in a linear pattern trending down

Medium-difficulty · SAT Math · Two-Variable Data & Models — Line of best fit. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.

Answer explanation

Choice B is correct. The equation representing a linear model can be written in the form y=a+bx, or y=bx+a, where b is the slope of the graph of the model and 0,a is the y-intercept of the graph of the model. The sterplot shows that as the x-values of the data points increase, the y-values of the data points decrease, which means the graph of an appropriate linear model has a negative slope. Therefore, b<0. The sterplot also shows that the data points are close to the y-axis at a positive value of y . Therefore, the y-intercept of the graph of an appropriate linear model has a positive y-coordinate, which means a>0. Of the given choices, only choice B, y=-1.9x+10.1, has a negative value for b , the slope, and a positive value for a , the y-coordinate of the y-intercept. 

Choice A is incorrect. The graph of this model has a y-intercept with a negative y-coordinate, not a positive y-coordinate.

Choice C is incorrect. The graph of this model has a positive slope, not a negative slope, and a y-intercept with a negative y-coordinate, not a positive y-coordinate.

Choice D is incorrect. The graph of this model has a positive slope, not a negative slope.